Electroresponsive device



March 8, 1938. A. J. MccoNNELL 0,673

ELECTRORESPONSIVE DEVICE Filed Nov. 21, 1956 2 Sheets-Sheet 1 Inventor: Andrew J. Mc Connell,

is Attorney March 8, 1938. A. J. MOCONNELL 2,110,673

' I ELECTRORESPONSIVE DEVICE Filed Nov. 21, 1936 v 2 She ets-Sheet 2 Fig. 7. Fig.8.

Inventor: Andrew J. Mc C'onne a. fiwlw by Attorney.

Patented Mar. 8, 1938 UNITED STATES z,uo,m mac'moassrossrva nsvrcr.

Andrew J. McConnell, Upper Darby, Pa assigns: to General Electric Company, a corporation of New York Application November 21, 1936. Serial No. 112,068

14 Claims.

My invention relates to improvements in electroresponsive devices and more particul arly to improvements in protective. relays for polyphase alternating current systems. In general, my invention relates to improvements in electroresponsive devices such as are disclosed and claimed in the copending application of D. C. Prince, Serial No. 112,067, filed November 21, 1936, for Electroresponsive device, and assigned to the same assignee as this invention.'\An object of my invention is to provide an improved multiple purpose electroresponsive device for polyphase circuits.

In the manufacture of polyphase wattmetric devices such as wattmeters and polyphase power directional relays, it has been customary to use two or more electric current conducting rotors such as disks, for example, on a single shaft with one or more separate electromagnetic means on each rotor ior producing a torque thereon. Such devices, becauseof their size, require a relatively large space and switchboard area. Also, since they have a low efilciency and high inertia, they do notmeet present day relay requirements for high torque and speed. Moreover, when in connection with a polyphase power directional relay it is desired to use voltage restraint, as disclosed in United States Letters Patent 1,883,839, of R. L. Webb, the construction becomes further involved by the addition of another electromagnetic torque Also, where both phase and ground fault protection involve the use of power producing means.

obtained either with or without voltage restraint and which may also include a ground power directional response. Further in accordance'with my invention, I provide an improved means for 50 eliminating certain undesirable torque eflects whereby to improve the accuracy of the response of e polyphase device having a single electric current conducting rotor'2 These and other objects of my invention will be better understood 55 from the iullowing description when considered in connection with the accompanying two sheets of drawings, and its scope will be pointed out in the appended claims.

In the accompanying drawings, Fig. 1 is a plan view of an electroresponsive device construction adapted to the carrying out of my invention; Fig. 2 is a sectional elevation on the line 2-2-of Fig. 1 as seen in a vertical plane after revolution of the diagonal portion of the section; Figs. 3, 4, and 5 are schematic views of devices similar to 10 that shown in Figs. 1 and 2 and are presented for explanatory purposes; Fig. 6 is a diagrammatic view illustrating schematically an electroresponsive device, such as shown in Figs. 1 and 2, connected in a polyphase circuit for directional re- 1 sponse to the polyphase power of the circuit; Figs. 7-11 are diagrammatic viewsillustrating various modifications of my invention.

The electroresponsive device illustrated in Figs.

1 and 2 is similar in construction to the electro- 20 responsive device disclosed in the copending application of V. E. Verrall, Serial No. 70,580, flied March 24, 1936, for Electroresponsive devices. As shown in Figs. 1 and 2, this device comprises a hollow magnetic stator I! having a plurality of 25 inwardly projecting salients IBI-lil, inclusive. Certain of these salients, those on the sides, for example, may be" integral with the stator and the others insertable in the stator. windings I! are provided for energizing the salients and also 30 a central magnetic member 18, concentrically positioned with respect to the ends of the salients, whereby to actuate a rotor is which is movable in the gaps between the salients and the stator ll, therotor being secured to a suitably iournaled shaft 20. The parts described are assem-.

bled as a unit between two end frames 2| and 22, which are held together by suitable means such as rivets 23. For reasons which will hereinafter appear and as disclosed in the copending application of E. H. Bancker, Serial No. 112,069, flied November 21, 1936, for Electroresponsive devices, one of the end frames, for example, the frame 2i which supports the stator i8, isprei'erably of magnetic material, as is also the supporting member or hub 24 on which the central magnetic member is mounted.

In Figs. 3, 4, and 5, which are intended as schematic representations of devices analogous to that shown in Figs. 1 and 2, similar reference numbers indicate corresponding parts. 'Inthe Prince application referred to herein, it is shown that ii the windings H on a device having six salients Iii-ll. i clusive, are energized by a set of threephase quantities 1, 2, 3, in the order 1,2, 2,1, 3,3, as indicated by the numbers at the ends of the respective windings I'I, then the rotating field poduced by the windings, on the salients I6I, I63, I65 is opposite in torque efiect to the rotating field produced by the windings I! on the salients I62, I64, I66. Other things being equal, the resultant torque on the rotor I9 is zero. Also as disclosed in the Prince application, this same action can be obtained with a simplified stator I5 having only four. salients for a threephase system of electric quantities, as shown in Fig. 4, or in general 2(n1) salients for an nwindings IT on the salients I6I, I 63, I65 is opposite to the direction of the rotating field produced by the salients I6], I61, I65. Other things being' equal, the resultant torque is zero and the rotor I9 is not actuated. The windings, I! may be energized by a set of three-phase voltages in a similar order, and the resultant torque on the rotor would be nothing.

If, however, it is desired to obtain a torque which is dependent, for example, on the sum of the products of the currents and the voltages of a polyphase system and have such torque independent of terms of the second order involving only current or voltage, then, as pointed out in the Prince application, alternate salients may be energized by the currents inthe three phase conductors of a three-phase system in the cyclic order I1, I2, I3, I2, for example, and the windings I! on the intermediate salients by three phase voltages of the system in the order E1, E2, E1, E3. In this way, the resultant torque is proportional to 2 E1 cos (+0), where E and I represent respectively'the currents and the voltages of the circuits, 5 the angle at which the current lags the voltage in the system, and 0 the angle of lead (current leading voltage) at which maximum torque occurs.

' In order more clearly to illustrate this torque feature in its application to a three phase circuit, I have shown schematically in Fig. 6, the connection of the windings of the device shown in Figs. 1 and 2 in a three-phase system. As illustrated, the three-phase system comprises a three-phase circuit whose phase conductors, designated 1, 2, 3 for simplicity in phase order, may constitute a feeder extending from a station bus 36. The respective phase currents may be derived through current transformers connected in the phase conductors and the voltages through a potential transformer 32 connected to the bus 30. In this figure, the current energized'windings are shown on the vertical and horizontal salients with reference toFig. 1, and the voltage energized windings on the diagonal salients with reference to Fig. 1. Only the windings are shown in this fig-' ure and for simplicity they will be designated by the corresponding numbers of their salients. The salients I6I, I63, I65, I61, are energized by the phase currents I1, I2, Ia, I2, respectively, so that the resultant torque on the rotor, not shown, of the windings on these salients is zero except for possible discrepancies due. to manufacturing limitations or tolerances. In other words, there are no second order terms involving the products of two currents to introduce an error in a desired voltage-current product function. The salients I62, I64, I66, I 68 are energized in accordance with on the rotor.

the phase voltages E23, E12, E23, and E31, respectively. The resultant torque on the rotor of the windings on these salients is accordingly zero. In other words, there are no second order terms involving the products of two voltages to introduce an error into the desired function of current voltage products, all as disclosed in the Prince application referred to. It has been found that these second order terms alone may introduce such an appreciable torque as to render a relay device unreliable for protective purposes unless such second order terms can be eliminated. Thus for example, these second order terms may amount to 15% of the actual power directional torque to which the device is supposed to respond.

There may be occasionsjhowever, when it is desired to obtain a torque balance for one of the groups of polyphase quantities and to have a predetermined bias or restraint effect derived from some other source, such, for example, as the other group of polyphase quantities. In this case, it is desirable that vacant salients, on which suitably energized windings may be placed'to obtain the desired effect, be available. In order to accomplish the torque balance feature and yet to have the available structure for a predeter mined restraintcharacteristic, I may arrange, in accordance with my-invention as shown in Fig. 7, to have "0 diametrically opposite salients I6I and I65 energized, for example, by the current difierences (IiI2) and (I2I3), respectively. In this way, there will be no second order term involving currents alone. The salients I62, I64, I66, and I68 may have their windings energized respectively by the voltages E23, E12, E23, and E31, and these will of themselves produce no torque The resultant torque of the salients shown is then a polyphase power directional torque without any second order terms. The unused salients I63 and I61, not shown in Fig. 7, may then be energized by such quantities as will produce the restraint desired for a particular application. These quantities may be system voltages where a predetermined relation is desired between a polyphase power directional torque and a torque dependent on certain voltages of the system from which the power directional torque is derived.

The connections shown in Fig. '7, as Well as some variants thereof, are given in the following Table I, although this table is by no means intended to be exhaustive of the possible arrangements which can beevolved without departing from the spirit and scope of my invention. In this table, as well as throughout this application, E used with the sub-numbers 10, 20, and 30 indicates star voltages and with 12, 23, and 31 delta voltages.

Table I Salient numbers .r... 161 162 163 164 165 166 167 168 Arrangement Electric quantities energizing windings E1; E1: Iz-Iz E En E25 12-13 E12 E31 I2-Ia E21 E1 E10 11-1 E30 E20 E20 L-II! E10 Em E3 11-13 E20 These difierent arrangements vary the angle of maximum torqueof the relay device. Obviously, the application of the different arrangementa is a matter or the characteristic desired for the type of protection in question. For example, arrangeture connection heretofore used with multiple disk polyphase relays, and arrangements B2 and v of the circuit breaker 33.

ment AI is suitable for ordinary transmission line protection, arrangement A2 may be applied to the control of-network protectors in low voltage alternating current systems, and arrangement A3 under certain other conditions. Arrangement BI is the equivalent of the so-called quadra- B3 are the equivalents of the adjacent connections also used with such relays.

In the embodiment of my invention shown in Fig.8, the circuit I, 2, 3 is illustrated as being connected to the bus 38 through a circuit breaker 33 having a trip coil 34. The relay device embodying my invention is schematically shown as having a circuit controlling member 36 which is arranged to control contacts in the circuit of the trip coil 34, whereby to control the opening The salients I6I, I63, I66, and I61 are energized by the line currents I1, Ir, 1:, I2, respectively, and consequently the torque due to the currents alone is zero. However, in accordance with my invention, in order to provide some voltage restraint, the salients I62, I64, I66, and I68 are energized by the voltages E23, E23, E12, E31, respectively. With this cyclic order of voltage energizations, the resultant torque due to voltage alone is not zero. Consequently, there is, in accordance with myrinvention, a predetermined voltage torque in addition to the power directional torque. Generally speaking, the connections are such that the voltage torque opposes the power directional torque under predetermined system conditions, for example, when power flows in a given direction, and assists when the power directional torque is reversed. The arrangement of the parts may be such that the voltage restraint predominates over the power torque under certain system conditions, for example, normal voltage conditions and power flow in a certain direction. As shown in Fig. 8, a relatively weak opening spring 36 may be used on the contact controlling member 35, but the strength of this spring is so small as to have substantially no efl'ect on the calibration or pick-up of the relay. Incase of three-phase faults .adjacent the relay location, the voltage windings become in effect short-circuited because the circuit voltages are practically zero. At such low circuit voltages, it is desirable that there be no net torque due to current alone. Ordinarily, some of the fluxes produced by the current windings may return through the salients which carry the voltage coils. Voltages are thus induced in the voltage coils. Consequently, currents flow in the voltage coils and the fluxes passing through these coils are modifled thereby. Because of the phase displacement between these modified fluxes and the 'current fluxes, small torques appear which are normally balanced. However, if these small torques are not balanced, an undesirable net'torque appears in one direction or the other. In accordance with my invention, I may balance these current bias torques by impedance adjustment of the circuits of the voltage coils through suitable means shown in Fig. 8 as adjustable resistors 31. Such balancing is particularly desirable for the three-phase fault condition, but the unbalance effect, even without the resistors, for example, may be substantially negligible ii there is anything like normal voltage on some of the voltage windings. I

Because of commercial limitations in manufacturing, certain variations or discrepancies may arise even though the windings arearrange'd in the theoretical order to balance out both the torques due to current alone and to voltage alone. .This lack of balance may be compensated by the use of the impedance device 31 in the circuits of the potential coils, or' the balance can be established by using flats or notches onthe fixed stator. Such a, notch is shown at 38 inFig. 1. By varying the position of theseflats or notches, the reluctance of the air gaps at the respective 'poles can be changed to. effect the desired balancing action.

The connections shownin Fig. 8- as well as certain variants thereof are given in the following Table II, but here again this table is by no means intended to be exhaustive of the possible arrangements which can be evolved with- -alent of the adjacent connections.

In the above table, arrangements DI, D2, and D3 are the equivalent of the usual connections of polyphase relays for transmission line protection except for the voltage restraint feature. Thus,.arrangement DI is, so far as the polyphase power torque is concerned, the equivalent of the so-called quadrature connection and similarly, arrangements D2 and D3 are the equiv- The connection DI is illustrated in'Fig. 9. The arrangement CI is suitable for the ordinary transmission line protection applications, although it is probably no better on ground faults than the ordinary quadrature connection. In other words, incorrect operation might result if the directional polyphase load torque is greater than the ground fault directional torque or when generation is present at one endof the line only. The arrangement C2 may be applied to the control of network protectors for low voltage alternating current circuits, and arrangement C3 may prove useful under certain other conditions. I

In order to obtain the maximum of protective features with the minimum amount of space and apparatus, I may provide, in accordance with my invention, a single unit device with only one current conducting. rotor which embodies not only the power directional feature but also the ground power directional feature, and may in addition include the voltage restraint feature or not, as desired. Such an embodiment of my invention is illustrated in Fig.- 10. In connection with the ground directional feature, some means of obtaining a zero phase sequence voltage E0 such as the Wye-open delta potential transformer 320 may be connected through the transformer 32 to be energized from the bus 38.

Inthis embodiment of my invention, the salients I6I, I65, I66, and I68 are energized respectively by the circuit currents I1, Ia, and the circuit voltages Em and E23. The fluxes in these salients co-operate to produce the polyphase power directional torque. The windings on the salients I62 and I64 are connected in the open delta of the transformer 320 so as to be energized by the residual or zero phase sequence voltage of the system. The polarity of the connection of the winding on the salient I62 is reversed. Polarity reversals are indicated by a minus sign in Table III and subsequent tables. The winding on the salient I63 is connected to be energized by the residual current of the circuit and for this purpose is connected in the residual lead of the current transformers 3|. To produce the desired ground torque effect, additional winding turns may be used in the windings on the salients I62, I63, and I64. The windings on these salients provide the fluxes whichproduce the ground directional torque. The salient I61 is energized by the voltage E21 reversed in polarity as indicated by the negative sign. The windings on the salients I66, I61, and I68 provide the desired voltage restraint. Examples of other ways in which the salient windings may be connected to provide polyphase and ground fault protection and also include voltage restraint are given in Table III, which, however, is not intended to be exhaustive of the possible arrangements which can be evolved without departing from the spirit and scope of my invention. In this table, 3E0 and 310 represent the actual ground fault voltage and current energizing the windings indicated and K is a proportionality factor which is dependent on design, for example, number of turns.

Table III Salient numbel'S 161 162 163 164 165 166 167 168 Arrangement Electric quantities energizing windings I; 3Eo 3X10 3E I2 Eu -Ea| En I -3Eo 3X10 3E 1: E -E z Eu I1 -3Eo .iKIo 3E0 11 Ear E:: Ex: 1 3E(; BKIo 3E0 I2, E10 ao 20 I1 3Eo BKIo 3E0 'I: E10 E10 E30 11 3Eo 3KIo 3E0 I: Eao 2o 10 1! o 3K1o 310 1: E1: -E:l n I1 3Io 3KIo 310 11 En --Eu n Ii Io 3KIo 310 12 ar 2: 1: 11 Iu 3K1c 310 I: E10 ao 20 11 -31!) 3KI0 310 I1 20 Eio E30 1 3Io 3KI0 311 1: E30 2o m In the E and F arrangements, the ground fault.

directional response is based on zero phase sequence current In and zero phase sequence-voltage Eo excitations, whereas in the G and H arrangements the ground' fault directional response is based on two separately energized zero phase sequence excitations which may be obtained in various ways well known to the art. The applications of the arrangements El, E2, and E3 are like those of the arrangements CI, C2, and C3 in Table II, except of course that there is the addition of the zero phase sequence power term to give the certainty of ground fault response regardless of magnitude of load power or location of generation. Similarly, the applications of the arrangements FI, F2, F3 are like those of the arrangements DI, D2, D3, Table I, except for the ground fault response feature. Whether the ground fault response is on the basis of current and potential or current and current is, as is well known to the art, a matter of choice for the particular application in hand. Accordingly, the arrangements Gand H may be chosen where ourrent-current excitation is desired. The application of the arrangements GI, G2, G3, is like that of arrangements CI, C2, and C3 in Table II, ex-

cept for the zero phase sequence power term to applications of the arrangements HI, H2, H3 are like those of arrangements DI, D2, D3, except for the ground fault response feature.

Fig. 11 illustrates another embodiment of my invention in which the resultant torque is a polyphase directional torque with voltage restraint. The diametrically opposite salients I6I and I65 are energized by the currents I1 and I2, respectively, so that there are no second order current terms to introduce any undesired current torque; the salients I62, I63, I64, I66, I61, I68 are energized by the voltages -Ez3, E31, -E12, E12, E31, and En, respectively. The resultant polyphase power directional torque arises from the action between the salients I6I and the adjacent salients I62 and I68 and between the salient I65 and the adjacent salients I 64 and I66. The restraining voltage torque arises from the action between the diametrically opposite salients I63 and I61 and the salients respectively adjacent these. Accordingly, with this arrangement, the result is a polyphase power directional torque with voltage restraint. Examples of other ways in which the salient windings may be connected to provide polyphase directional torque with voltage restraint are given in Table IV, which, however, is not intended to be exhaustive of the possible arrangements which can be evolved without departing from the spirit and scope of my invention.

The application of these respective arrangements LI, L2, L3 is the same as the arrange ments CI, 02, and C3, as shown in Table II.

In the various modifications of my invention and particularly those involving the use of zero phase sequence quantities, it will be observed that the flux produced by a coil crosses the air gap,

thereby entering the rotor, and may return by any path in inverse proportion to the reluctance of that path. Such path may be the salient of another coil and consequently extraneous torques may appear. These are substantially eliminata, however, by making the end plate 2 I, which supports the stator I8, as well as the hub suppo 24 therefor, of magnetic material, as disclose in the Bancker application supra. In this way, there is provided a shunt flux return path whereby the residual fiuxes can return by innocuous paths without reacting upon other fluxes to produce unwanted torques.

While I have shown and describedmy invention in considerable detail, I do not desire to be limited to the exact arrangements shown, but seek to cover inthe appended claims all those modifications that fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a polyphase alternating cur- I rent system and an electroresponslve device comexisting polyphase quantities derived from said' system including a multipole magnetic member,

member in accordance with the magnitudes of and the phase displacements between predetermined electric quantities of two groups of cowindings thereon connected to be energized by said groups of quantities in a predetermined or-' der to provide a torque proportional to a predetermined function of said quantities, certain of said windings being energized by predetermined quantities from one group to provide a counter torque opposed to said first torque under'predetermined conditions of the system.

2. In "combination, a polyphase alternating current system, an electroresponslve device comprising a single rotor having a closed electric current conducting path and means for actuating said rotor in accordance with the magnitudes of and the phase displacements between predetermined electric quantities oi. 'two groups of coexisting polyphase quantities derived from said system including a magnetic member comprising a plurality of radially disposed salients having their extremities concentric with the conducting path of said rotor, means for energizing only two diametrically opposite salients'by quantities from one polyphase group including windings on said two salients, the torque eflfect oi said windings alone on said rotor being substantially nothing, and windings on other salients'connected to be energized in a predetermined orderby electric quantities from the other polyphase group, the resultant torque effect of all of said windings on said rotor being proportional to the sum of the products of the quantities energizing adjacent salients and the phase displacement between said quantities.

3. In combination, a polyphase alternating current system, an electroresponslve device comprising a single rotor having a closed electric current conducting path, and means for actuating said rotor in accordance with the magnitudes of and the phase displacements between prede-v termined electric quantities of two groups of coexisting polyphase quantities derived from said system, including a magnetic membercomprising. a plurality of radially disposed salients having their extremities'concentric with the conducting path of said rotor, windings on certain of said salients connected to be energized in a predetermined order by quantities from one of said polyphase groups, the torque eflect of said windings alone being substantially zero, and

windings on certain other salients connected to be energized in a predetermined order by quantitles from the other polyphase group to exert a torque on said rotor and the resultant torque effect on the. rotor of the interaction of the windings energized by the polyphase quantities in the two groups being dependent upon the product of the quantities energizing adjacent salients and the phase displacement between said quantities.

4. In combination, an n-phase alternating cur tem, the resultant torque eilect of said windings on said 'rotor being zero, and windings on the other salients connected to be energized in a predetermined order by'another set of n-phas'e electric quantities or said system to exert a torque effect on said rotor, the resultant torque effect of adjacent windings energized by quantities from said two different sets of polyphase quantities being dependent on the summation of the products of the quantities energizing said windings and the angular displacements of said quantities. I

5. In combination, a three-phase alternating current system and a relay comprising a single rotatable current conducting member, electromagnetic means for actuating said member in accordance with a component'ot the polyphase power of the system including a multipole magnetic member and windings thereon connected tobe energized by the currents and the voltages of the system in a predetermined order, certain of said windings being energized by predetermined voltages of the system to provide a torque opposed to said power torque under predetermined system conditions.

6. In combination, a polyphase alternating current system and an electroresponslve device comprising a single rotatable current conductingmember and electromagnetic means for actuating said member in accordance with the magnitudes of and the phase displacements between the currents and the voltages of the system including a multipole magnetic member and windings thereon connected to be energized by said currents and voltages in a predetermined order to provide a torque dependent upon the polyphase power or the system, and a voltage restraint torque under predetermined conditions of the system.

7. In combination, a polyphase alternating current system and a device comprising a single rotatable current conducting member, electromagnetic means for actuating said member in accordance with the magnitudes of and the phase displacements between the currents and voltages of said system including a multipole magnetic member and windings thereon connected -to be energized by said currents and voltages ina predetermined order to provide a torque which is proportional to a component of the power of said system, certain of said windings being energized by predetermined voltages of the system to provide a torque opposed to said power torque under predetermined conditions of the system.

8. In combination, a three-phase alternating current system, an electroresponslve device comprising a single rotor having a closed electric current conducting path and means ior'actuating said rotor in accordance with the polyphase power of said system including a magnetic member comprising a plurality of radially disposed salients having their extremities concentric with the conducting path of said rotor, windings on certain of said salients connected to be energized in a predetermined order by currents derived from said system currents, the torque efiect of said current energized windings alone being substantially zero and windings on certain other salients value and the resultanttorque effect on the rotor v of the interaction of the current and voltage energized windings being dependent on acomponent 0f the polyphase power or said system.

9. In combination, a polyphase alternating current system and an electroresponsive device comprising a single rotatable current conducting member and electromagnetic means for actuating said member in accordance with the magnitudes of and the phase displacements between the currents and the voltages of the system including a multipole magnetic member and windings thereon connected to be energized by said quantities in a predetermined order to provide a torque dependent on the polyphase power of the system and the zero sequence power of the system.

10. In combination, a polyphase alternating current system and an electroresponsive device comprising a. magnetic stator having a plurality of inwardly projecting salients, a magnetic member centrally positioned relatively to and spaced from the inner ends of said salients, a rotor of electric current conducting material between said central magnetic member and the inner ends of said salients, means for actuating said rotor in accordance with the polyphase power of the system and the zero sequence power of the system including windings on said stator connected to be energized by the currents and the voltages of the system in a predetermined order, and a shunt magnetic path ,for the residual flux of the windings producing the zero sequence power torque.

11. In combination, a three-phase alternating current system and a relay comprising a single rotatable current conducting member, electromagnetic means for actuating said member including a multipole magnetic member and windings thereon connected to be energized by said quantities in a predetermined order to provide a torque dependent on a component of the polyphase power of the system and a voltage restraint torque opposed to said polyphase power torque under predetermined system conditions and further windings on said member connected to be energized in accordance with zero phase sequence quantities of the system to provide a torque dependent on the zero phase sequence'power of the system. I

12. In combination, a polyphase alternating current system and an electroresponsive device comprising a single rotatable current conducting member, electromagnetic means for actuating said member in accordance with the magnitudes of and the phase displacements between the currents and the voltages of the system including a multipole magnetic member and windings thereon connected to be energized by said quantities ina predetermined order to provide a torque dependent on a component of the polyphase power of the system, and a voltage restraint torque opposed to said polyphase power torque under predetermined conditions of the system, and further windings on said member energized from said system to providea third torque dependent on the zero sequence power of the system.

13. In combination, a polyphase alternating current system, an electroresponsive device comprising a movable member having an electric current conducting path, and means for controlling the movement of said member in accordance with a zero phase sequence quantity derived from said system including a magnetic member having a plurality of salients; a winding on one of said salients energized by said zero phase sequence quantity and a return magnetic path independent of said magnetic member for the flux induced in said salient by said zero phase sequence quantity. 14. In combination, two polyphase systems of alternating current quantities, an electroresponsive device comprising a single rotatable electric current conducting member, and means for actuating said rotatable member in accordance with the magnitudes of and the phase displacements between predetermined quantities of said two systems including a magnetic member comprising a plurality of radially disposed salients having their extremities concentric with said rotatable member, means for energizing each of two diametrically opposite salients by a function of at least two quantitiesfrom one polyphase group, including windings on said two salients, the torque eifect of said windings alone on said rotatable member being substantially nothing, and windings on other salients connected to be energized in a predetermined order by electric quantities from the other polyphase group, the resultant torque efiect of all of said windings on said rotor being proportional to the sum of the products of the quantities energizing adjacent salients and the phase displacement between said quantities.

' ANDREW J. MCCONNELL. 

